Field of the Invention
The invention relates to an electromagnetic release for a protective circuit breaker, in particular, for a residual current circuit breaker.
Conventionally, a release used for a network- or mains-voltage-independent residual current protective device was based upon a magnetic circuit on the compensation principle. A U-shaped magnetic yoke is provided. A coil is wound around one limb of the yoke. On the yoke there is a permanent magnet, and the two limbs of the yoke are covered by an armature, which is spring loaded into the disconnect or release position. The permanent magnetic acts such that the armature, in the quiescent state, is attracted against the free ends of the limbs of the yoke. If a fault current occurs, then the magnetic flux generated by the fault current acts against the flux generated by the permanent magnet, so that the spring overcomes the attraction force and pivots the hinged armature into the opening position.
In addition to such holding-magnet releases, blocking magnet releases have also been used, but these are used much less frequently. The coil winding is connected to a secondary winding of a summation current transformer, whose primary winding is formed by the live conductor. As soon as a fault current occurs, current is applied to the coil of the release in a conventional manner, and the release responds.
In the event of an adhesion layer being present between the armature bearing face and the surface of the pole, the excess force from the spring, which moves the armature in the disconnect direction, is sometimes inadequate to break the contact between the armature and the pole face, and, in this example, the release fails.
It is necessary for the pole surface to be polished in order to achieve an adequate magnetic adhesion force. The pole face and the air gap present are extremely critical variables. Therefore, for example, applying a protective layer as a measure against sticking cannot be used. Furthermore, the geometry of the configuration makes automated production increasingly difficult because the individual parts have to be produced with high precision and monitoring, and have to be assembled with a great deal of personal, i.e., manual, effort, under clean-room conditions.
Because sticking sometimes cannot be avoided, the user is recommended in general terms to operate a test push-button once a month in order to check the serviceability of the release. When the test push-button is actuated, a fault current is simulated, so that the release responds and the residual current circuit breaker opens.
Because regular testing of a residual current circuit breaker is often not performed, in particular, in a domestic household, consideration has been given to avoiding possible sticking of the hinged armature in the event of a fault current. To such an end, carrying out automatic testing with automatic opening has been proposed. Such automatic testing can be disadvantageous to the extent that current interruptions are produced as a result of the automatic opening of the circuit breaker. Such interruptions are mostly undesired and present problems, which will not be further discussed.
In addition, there are also additional devices associated with the release in the form of additional releases. The additional releases are configured, for example, as piezoelectric elements or as electromagnetic releases. However, such additional elements and additional releases increase the outlay on the production of a residual current circuit breaker.
It is accordingly an object of the invention to provide an electromagnetic release that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that prevents sticking to the greatest possible extent, so that a release can be used readily even in a residual current circuit breaker for unlatching a switching mechanism. In particular, the electromagnetic release of the invention has fewer parts and has a simpler configuration. Accordingly, automatic production is improved and manufacture time and cost are reduced.
With the foregoing and other objects in view, there is provided, in accordance with the invention, an electromagnetic release, including a yoke, a spring disposed in the yoke and having a spring force, a plunger loaded by the spring in a release direction, a permanent magnet configuration associated with the yoke and the plunger and having a magnet flux, an attraction force, and an active range, a coil associated with the yoke and generating in the yoke a magnetic coil flux opposed to the magnet flux such that, when the magnetic coil flux is released, the spring force overcomes the attraction force of the permanent magnet configuration, and at least one pole shoe assigned to the yoke and the plunger and having an active range, the at least one pole shoe and the permanent magnet configuration conducting the magnetic coil flux to the plunger such that, in a first position of the plunger, the plunger is located in the active range of the permanent magnet configuration and in the active range of the at least one pole shoe, and both the magnetic coil flux and at least part of the magnet flux run through the plunger, and, in a second position of the plunger, the plunger is located at least partly in the active range of the at least one pole shoe, and the magnet flux runs through the yoke, the plunger, and the permanent magnet configuration.
According to the invention, at least one permanent magnet and at least one pole shoe are assigned to the yoke and to the release plunger such that, in a first position, the plunger is located in the active range of the permanent magnet and of the pole shoe and, in a further position, is located only in the active range of the pole shoe. Accordingly, in the first position, both the magnetic flux from the coil and that from the permanent magnet, the latter at least partly, run through the plunger. In the second position, the magnetic field generated by the permanent magnetic runs through the plunger, the permanent magnet and the yoke, so that in the latter position a stable working point of the permanent magnet is maintained.
In accordance with another feature of the invention, the yoke has two yoke sections running parallel to each other, to which the plunger axis runs perpendicularly. The plunger reaches through one of the yoke sections (first yoke section), forming an air gap, whose width remains constant during the entire movement of the plunger. Thus, a change in the force on the plunger is avoided.
In accordance with a further feature of the invention, in its first position, the plunger bears against the inner face of the second yoke section. Due to the configuration of the release, the release force being sufficiently high, processes involving sticking of the plunger to the second yoke section, which could give rise to an ineffective release, are avoided.
In accordance with an added feature of the invention, to provide assistance, the plunger can be coated with an anti-adhesion layer on its actuating face facing the second yoke section. The layer may be made of a material that is as corrosion resistant as possible, in particular of nickel or a nickel alloy.
In accordance with an additional feature of the invention, the plunger can preferably have a ridge; the spring is then inserted between the pole shoe and the ridge.
In accordance with yet another feature of the invention, the yoke is a closed ring and has limbs disposed opposite the first of the two yoke sections, the coil is disposed inside the yoke, and the plunger, the permanent magnet configuration, and the at least one pole shoe are disposed inside the coil, the permanent magnet configuration bears against the inner face of the second of the two yoke sections, the at least one pole shoe is disposed coaxially with the permanent magnet configuration, the permanent magnet configuration and the at least one pole shoe accommodate the plunger therebetween in a quiescent state of the coil, and the plunger reaches through the limbs.
In accordance with yet a further feature of the invention, the yoke has at least a U-shape, at least one web, and at least one limb, the coil surrounds the at least one web, and the at least one limb forms the first of the two yoke sections and covers the end face of the plunger.
In accordance with yet an added feature of the invention, the U-shaped yoke has an integral further yoke piece, the at least one limb is two limbs forming two parallel yoke webs, the permanent magnet configuration and the plunger bear against one of the two yoke webs, and the plunger reaches through another of the two yoke webs.
According to a particularly advantageous refinement of the invention, the yoke can have a pot, into which the annular coil, the permanent magnet configuration constructed as an annular permanent magnet, the annular pole shoe, the spring constructed as a helical spring and the plunger can be inserted in the following way. The plunger is surrounded both by the permanent magnet and by the pole shoe and the spring. The pot is closed by a cover, through which the plunger reaches. In order to form the release, the cover serves as the first yoke section and the bottom of the pot forms the second yoke section.
In accordance with yet an additional feature of the invention, there is provided a sleeve of insulating material, the bottom of the pot has an inner side, and the at least one pole shoe and the permanent magnet are pressed against the inner side of the bottom of the pot with the sleeve of insulating material.
Another configuration considerably simplifies the manufacture of the release. It is possible to prefabricate the configuration of the permanent magnet configuration, pole shoe, coil former and coil and simply insert it into the pot. In accordance with still another feature of the invention, the at least one pole shoe and the permanent magnet are cast into a cylindrical body to form a coil former, such that the coil, the coil former, the at least one pole shoe, and the permanent magnet form a pre-assembled unit.
In accordance with yet an additional feature of the invention, the permanent magnet has at least one of the group consisting of a circumferential ridge and a groove holding the permanent magnet on the coil former in a form-fit.
In accordance with again another feature of the invention, the plunger is moveable away from the one of the two yoke webs at most to place the end face of the plunger essentially in an area of the at least one pole shoe to ensure a flux through the at least one pole shoe, the plunger, and the yoke. This configuration provides a further advantage. If, the end of the plunger is located in the area of the pole shoe when the release, serving as a residual current release, has reached its release position, then the working point of the permanent magnet remains approximately constant in any possible position, because, in any possible position, a magnetic flux through the permanent magnet, the pole shoe, the plunger and the yoke is ensured.
In accordance with again a further feature of the invention, the permanent magnet configuration has an axial length, and a distance the end face of the plunger assumes from the one of the yoke webs when driven is greater than an axial length of the permanent magnet configuration.
In accordance with again an added feature of the invention, a released position is defined by the plunger being essentially located only in an area of the at least one pole shoe, and in the released position the permanent magnet configuration is magnetized by a current pulse through the coil. An advantage of this feature is provided by the released position of the coil, wherein a flux through the permanent magnet is generated, so that the permanent magnet can be magnetized by a pulse originating from the coil. As a result, it is no longer necessary to install the permanent magnet in the premagnetized state or to magnetize it from the outside in special, complicated devices. Instead, the permanent magnet is magnetized only when it has been mounted in the release.
In accordance with a concomitant feature of the invention, there is also provided a residual current circuit breaker electromagnetic release.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an electromagnetic release, it is, nevertheless, not intended to be limited to the details shown since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.